Note - You can only wear a sacred Tulsi kanthi mala if you follow these four regulative principles.

1- No Intoxication and no Tea & coffee      

2- No meat eating and no Onion & Garlic

3- No Gambling                                                         

4- No Illicit Sex (Sex outside Marriage)

It is said in the Padma Purana - Those who wear the Kanthi Mala of Tulsi and do tilak of sandalwood at 12 places on their body. Worshipers of Lord Vishnu (Krishna) and are called Vaishnavas. His presence makes the whole universe pure and with his presence such devotees can make any place auspicious like Vaikuntha.

It also ensures the maintenance of spiritual purity while keeping away Evil spirits. Tulsi is regarded best for worshipping Lord Vishnu, Krishna, and Balram,Ram

It is also said in Skanda Purana - "Those who rub their foreheads and bodies with gopi sandal and wear a necklace of tulsi garland around the neck, they cannot even find the emissary of Yamraj.